Acclimations of macroalgae as reflected in phothosynthetic parameters derived from PAM fluorometry,and possible implications for abundance patterns / Saroussi, Shai

Public ISBD Faire une suggestion d'achat Titre : Acclimations of macroalgae as reflected in phothosynthetic parameters derived from PAM fluorometry,and possible implications for abundance patterns Type de document : texte imprimé Auteurs : Saroussi, Shai, Auteur Importance : pp. 377-383 Langues : Anglais (eng) Index. décimale : 577 Ecologie Résumé : The presences of the common macroalgae Ulva sp. and Jania rubens vary between seasons along the Israeli Mediterranean intertidal zone. To reveal some of the potential acclimation mechanisms of these algae, we examined their photosynthetic traits during the year using rapid light curves (RLC) derived from pulse amplitude modulated (PAM) fluorometry. In addition, the relationships between those photosynthetic traits and the relative abundances of the two algae were investigated. Ulva sp. showed high maximal electron transport rates (ETRmax) (49.7-68.8 umol electrons m-2 s-1) and onsets of light saturation values (Ek) (75.8—85.6 ,umol photons m-2 s-1) in the winter months of December-February, while low values were found in the summer months of June-July (5.2-20.6 umol electrons m"2 s"1 and 6.0-23.7 {imol photons m-2 s-1, respectively). At noon time (during the highest irradiance of the day), the maximal effective quantum yield (Y0) did not vary significantly during the year. These results indicate that seasonal irradiance influences the number of reaction centres per thallus area. Both algae showed depressions in Y0 at noon (23.8% for Ulva sp. and 20.3% for Jania rubens}, indicating an efficient non-photochemical quenching mechanism. A positive correlation between the relative abundance and the photosynthetic parameter Y0 was found for Jania rubens when Y0 was sampled in the morning or noon, indicating that growth rate and primary production for this alga can be estimated from RLCs. No such correlation was found for Ulva sp., indicating that, in addition to photo-synthetic traits, the relative seasonal abundance of this alga is influenced by other factors such as grazing and/or catastrophic events. Acclimations of macroalgae as reflected in phothosynthetic parameters derived from PAM fluorometry,and possible implications for abundance patterns [texte imprimé] / Saroussi, Shai, Auteur . - [s.d.] . - pp. 377-383. Langues : Anglais (eng) Index. décimale : 577 Ecologie Résumé : The presences of the common macroalgae Ulva sp. and Jania rubens vary between seasons along the Israeli Mediterranean intertidal zone. To reveal some of the potential acclimation mechanisms of these algae, we examined their photosynthetic traits during the year using rapid light curves (RLC) derived from pulse amplitude modulated (PAM) fluorometry. In addition, the relationships between those photosynthetic traits and the relative abundances of the two algae were investigated. Ulva sp. showed high maximal electron transport rates (ETRmax) (49.7-68.8 umol electrons m-2 s-1) and onsets of light saturation values (Ek) (75.8—85.6 ,umol photons m-2 s-1) in the winter months of December-February, while low values were found in the summer months of June-July (5.2-20.6 umol electrons m"2 s"1 and 6.0-23.7 {imol photons m-2 s-1, respectively). At noon time (during the highest irradiance of the day), the maximal effective quantum yield (Y0) did not vary significantly during the year. These results indicate that seasonal irradiance influences the number of reaction centres per thallus area. Both algae showed depressions in Y0 at noon (23.8% for Ulva sp. and 20.3% for Jania rubens}, indicating an efficient non-photochemical quenching mechanism. A positive correlation between the relative abundance and the photosynthetic parameter Y0 was found for Jania rubens when Y0 was sampled in the morning or noon, indicating that growth rate and primary production for this alga can be estimated from RLCs. No such correlation was found for Ulva sp., indicating that, in addition to photo-synthetic traits, the relative seasonal abundance of this alga is influenced by other factors such as grazing and/or catastrophic events.

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